Field of the Invention
The present invention relates to a honing method by which an arcuately shaped inner circumferential surface, in which a discontinuous portion is provided between both ends thereof in a circumferential direction, is subjected to grinding. The present invention further relates to an inner cam having a substantially C-shaped cross section, the inner circumferential surface of which is subjected to grinding by such a honing method.
Description of the Related Art
In the case of finishing an inner circumferential sliding surface of a cylindrical workpiece, preferably a honing process is adopted from the standpoints of facilitating mass production and achieving superior lubrication performance. A honing head that is used for honing is shaped substantially in the form of a cylinder, and a plurality of rod-shaped grindstones, which extend along the axial direction, are attached at intervals along the circumferential direction thereof. The honing head is inserted into the interior of a workpiece so that the direction of extension of the grindstones lies along an axial center, and while the grindstones are rotated, grinding is enabled by placing the grindstones in contact with the workpiece and applying an appropriate surface pressure to the inner circumferential surface of the workpiece.
In such a honing process, in the case that a groove or an opening or the like is formed to extend along the axial center on the inner circumferential surface of the workpiece, or stated otherwise, in the case that the inner circumferential surface of the workpiece is arcuately shaped with a discontinuous portion being provided between both ends in the circumferential direction of the workpiece, a concern arises in that it becomes difficult to perform grinding satisfactorily. More specifically, if the distance between both end portions that form the discontinuous portion is greater than the width of the grindstones, the grindstones will enter into the discontinuous portion during grinding. Consequently, since a deviation occurs between the axis of the workpiece and the center of rotation of the honing head, it can be assumed that it will become difficult to grind the inner circumferential surface of the workpiece evenly, and thus machining precision is lowered.
Thus, according to Japanese Laid-Open Patent Publication No. 58-155167, when honing an inner circumferential surface of a workpiece having a groove formed therein with grindstones having a width narrower than the width of the groove, the following method for suppressing a reduction in machining accuracy has been proposed. More specifically, a plurality of workpieces are stacked and retained in such a manner that positions of the grooves in the circumferential direction differ from each other, and honing is performed thereon simultaneously by bringing the grindstones into contact with inner circumferential surfaces of the workpieces. In accordance therewith, the grindstones as a whole are prevented from entering into the grooves, and a deviation between the axial centers of the workpieces and the center of rotation of the honing head is suppressed.